import std.algorithm, std.conv, std.range, std.stdio, std.string; import std.math; // math functions void main() { auto k = readln.chomp.to!int; auto n = readln.chomp.to!int; auto pi = primes(n).assumeSorted!"a <= b".upperBound(k).array; auto hi = pi.map!hash.array; auto maxL = 1, maxP = pi[0], i = 0, j = 0; auto buf = new bool[](10); buf[hi[0]] = true; while (true) { if (++j >= pi.length) break; if (buf[hi[j]]) { foreach (ref h; hi[i..j].until(hi[j], OpenRight.no)) { buf[h] = false; ++i; } } auto len = j - i + 1; if (len >= maxL) { maxL = len; maxP = pi[i]; } buf[hi[j]] = true; } writeln(maxP); } int hash(int n) { static int[int] memo; if (n in memo) { return memo[n]; } else if (n < 10) { return memo[n] = n; } else { auto r = 0; for (; n > 0; n /= 10) r += n % 10; return memo[n] = hash(r); } } int[] primes(int n) { auto sieve = new bool[]((n + 1) / 2); sieve[] = true; foreach (p; iota(1, (n.to!real.sqrt.to!int - 1) / 2 + 1)) if (sieve[p]) foreach (q; iota(p * 3 + 1, (n + 1) / 2, p * 2 + 1)) sieve[q] = false; auto r = sieve.enumerate .filter!("a[1]") .map!("a[0]").map!("a * 2 + 1") .map!(to!int).array; r[0] = 2; return r; }